Someone asked a question on the MCForum (which is the discussion site for the Erotic Mind Control Story Archive) about pacing. I started to answer, it got out of hand, and I if I'm writing that much, darn it, I'm getting a blog post out of it. Below, my screed:
The most common pacing problem I see is breathlessness. "And then... and then... and then... and then..." Sometimes the characters need a break, so the reader can relax a second and feel like something has happened and is now over before they move on. Build up, resolve, segue, repeat.
Here's a fairly simple and obvious way to see if you think your pacing is on. Compare how fast the story is progressing with how excited the characters are. (If the characters are excited all the time, either you're writing flash fiction and pacing isn't really a big deal, or see "breathlessness" above.) If the characters are excited but nothing seems to be happening very fast, you're progressing too slow. If the characters aren't excited but all kinds of stuff is going on, either you're writing Sherlock Holmes or you're progressing too fast. If the story is running, the characters should be too! If the story is moving slowly, the characters should be doing more thinking than acting.
A not-so-obvious thing that can indicate pacing problems is the need for infodumps. If you get your characters into a situation where they are having some kind of confrontation or major plot development is happening and you have to pause for a page to explain a bunch of background stuff, you didn't build up the story enough before you initiated the event. Go back and spread it out in the lead-up to the big scene. Once a major scene starts, we should know all we have to know to follow the events. (Although critical revelations at the crux or after the fight ends are perfectly respectable writing technique.)
As regards pacing and the actual mind control content, a couple of thoughts:
1) Show, don't tell. I know, I know. People always say that and it's just irritating. But seriously. "X's mind control machine works by doing A, B, and C." is not as good as, "X hooked up the mind control machine and threw the first switch, which caused A to happen, making the victim squirm helplessly*. When the A cycle was complete, she turned the B dial all the way up..." etc, etc. You're still telling, but you're telling in the context of actually doing it.
2) Try to have a mechanism and method in mind when you develop your mind control means, and be consistent about it. Keep in mind that the mechanism and method will dictate your pacing and exposition. Be consistent, and keep in mind the limitations of the method. It is perfectly okay to use magic or ultratech (in fact, unless you're Wiseguy and you can write amazingly convincing conventional hypnosis stories, you kinda have to.) But however it works, be consistent and allocate the amount of time and thought (and corresponding plot development) to it that it reasonably requires.
For instance, in my novel "Maestro," the Pitchpipe (the mind control machine) requires fairly extensive preparation/execution time. (A significant portion of the book is just the Maestro inventing the thing.) Time to let it work and the opportunity to get the subject into it and not be interrupted are sort of secondary antagonists to the Maestro. It adds tension to hear the description of it working knowing it could be interrupted or discovered. And I knew all along that the Pitchpipe would lend itself to long descriptions of its function which people who like that kind of thing, um, like. :)
On the other hand, my novella "Sorority Saturday" involves a MC machine which is literally a Little Black Box that goes "Flash!" and the subject is enthralled. It too has limitations, some of which are obvious in the story (it has limited range, the effects don't last long) and some of which aren't (what a subject can and can't be told to do are never explained, but there are restrictions, and I know what they are.) That was me getting down and rolling around in it, so to speak. He goes in, he takes what he wants. Over half the book is basically an extended orgy scene. But even then, there are build-ups and resolutions, pauses and breaks.
Incidentally, if ultratech and/or intricate method development aren't your thing, this latter is the way to go. The Pitchpipe appeals to the sort of reader who demands believability. It's totally consistent with the known laws of nature, and wouldn't require the suspension of disbelief other than to assume that one man could make the kind of breakthrough it requires to actually build. The Little Black Box is nonsensical. It runs on what one might call "handwavium," and any illusionist will tell you that the key to success in sleight of hand, or sleight of mind, is not letting people think too hard about what you're actually doing. Extensive development exposition would bore people who don't care and turn off people who do.
It helps to know going in which basic sort of MC you're going to have. If the MC is fast-acting, try to pace your whole story fast, because you're trying to appeal to the sort of reader who wants to get right to it. If the MC is slow and elaborate, try to write it into a longer story so that the non-MC content doesn't feel tacked on. (Incidentally, while many people do seem to have strong preferences, these are not mutually exclusive categories. I like both kinds and will happily read either so long as they are well-written.)
Man, that got long. Sorry. :) I hope it's helpful.
*When in doubt, make someone squirm helplessly. To paraphrase Admiral Nelson, "No mind controller can do very wrong by making someone squirm helplessly."